1. Field of Invention
The present invention relates generally to optical network systems. More particularly, the present invention relates to enabling a path trace such as a J1 trace to be monitored even when a signal such as a synchronous transport signal is transmitted on a protection path.
2. Description of the Related Art
The demand for data communication services is growing at an explosive rate. Much of the increased demand is due to the fact that more residential and business computer users ate becoming connected to the Internet. Furthermore, the types of traffic being carried by the Internet are shifting from lower bandwidth applications towards high bandwidth applications which include voice traffic and video traffic.
To address the demand for data communication services, the use of optical networks, such as a synchronous optical network (SONET), is becoming more prevalent. As will be appreciated by those skilled in the art, a SONET network is an example of a time division multiplexed (TDM) network. TDM networks generally allocate single lines to be used amongst multiple data streams or connections. The single lines may each be divided into slots of time during which each user has access to the single lines.
A network such as a TDM network is generally designed to ensure that information may be transferred between nodes within the network. Often, within a network, information is transferred between two specified nodes, i.e., a source node that sends information and a destination node which receives information. When information is to be sent between a source node and a destination node, a circuit path between the two nodes must be computed so that leased line services may be provided.
In general, a network may include at least one bi-directional line switched ring (BLSR). A BLSR typically allows data traffic to be sent in opposite directions. That is, for a bi-directional ring, traffic is often routed such that both directions of a two-way connection travel along the ring using the same ring nodes, but in opposite directions. A BLSR may typically include either two fibers or four fibers. As will be appreciated by those skilled in the art, a two fiber BLSR is a ring in which traffic is normally routed in both directions, i.e., in a clockwise direction and a counter-clockwise direction. On the other hand, network elements within a four fiber BLSR may be arranged to include two working fibers which may enable traffic to be routed in opposite directions and two protection fibers between two network elements.
FIG. 1a is a diagrammatic representation of a four fiber BLSR which includes four network elements. As shown, a BLSR 100 includes network elements 104 which are connected by working fibers 108 and protection fibers 112. Network elements 104 may generally be line terminating equipment or path terminating equipment, depending upon where circuit paths within BLSR 100 start and end. By way of example, for a circuit 124 which has a start point 116 at network element 104a and an end point 120 at network element 104c, network elements 104a, 104c may include path terminating equipment, while an intermediate network element 104b within circuit path 124 may include line terminating equipment.
Circuit path 124 may be defined on working fibers 108 between network element 104a and network element 104b, as well as between network element 104b and network element 104c. For example, a signal such as a synchronous transport signal (STS) may be sent in a clockwise direction, or an east-to-west direction, between network element 104a and network element 104c using working fiber 108a and working fiber 108b. An STS, as will be appreciated by those skilled in the art, may include a “name tag” which allows the STS to be differentiated from other STSs. The name tag may be a J1 byte or string, i.e., J1 bytes which are concatenated to form a string, that includes substantially any suitable identifying information, e.g., an address or an interface name, which may enable an STS to be identified. Specifically, a path trace identifier may be transmitted as part of a J1 byte in a path overhead, and may carry information such as a remote hostname, an interface name, and an internet protocol (IP) address. Typically, J1 information included in a J1 string may include up to sixty-four bytes.
After a circuit such as circuit path 124 is provisioned, network element 104a, which includes path terminating equipment, may transmit a path trace identifier as part of a J1 string along circuit path 124. That is, network element 104a may transmit J1 path trace information to other network elements included in circuit path 124 as part of an STS. Transmitting a J1 string as a part of an STS enables network elements 104 to determine the integrity of the STS when J1 monitoring is enabled, and, hence, to raise an alarm such as a TIM-P alarm when the J1 received by network elements 104 on circuit path 124 is not as expected.
In order to enable the J1 string embedded in the STS to be used to check the integrity of the STS, when circuit path 124 is provisioned, J1 information may be transmitted to substantially all network elements 104 included in circuit path 124. The transmitted J1 information may be broadcasted such that the information is received by a control card included in each network element 104 included in circuit path 124. The control card may then store the J1 information in a table of J1 information associated with substantially all circuits which use the network element 104 which houses the control card. The control card in each network element 104 included in circuit path 124 may then provide the J1 information to working linecards in its respective network element 104, as will be discussed below with respect to FIG. 2.
If J1 monitoring is enabled, when an STS which includes J1 information is sent from network element 104a to network element 104b on one of working fibers 108a, 108e, a monitor (not shown) which is associated with network element 104b determines whether the J1 information included in the STS matches the J1 information which was sent when circuit path 124 was provisioned. Irregardless of whether the J1 information matches, it should be appreciated that traffic may be forwarded to network element 104c on one of working fibers 108b, 108f. When the J1 information does not match, then an alarm may be raised which prompts a network administrator to take action with regards to an unexpected STS.
At times, working fibers 108 or network elements 104 may fail such that circuit path 124 between start point 116 and end point 120 may have to be altered. By way of example, when working fiber 108b fails, then if a suitable one of protection fibers 112b, 112f is available, a protection circuit path 124′ between start point 116 and end point 120 may be use to send STS, as shown in FIG. 1b. Specifically, protection circuit path 124′ may effectively include one of working fibers 108a, 108e, and one of protection fibers 112b, 112f. As will be appreciated by those skilled in the art, this is called a span switch, as traffic is switched to the protection span.
As will be discussed below with respect to FIG. 2, protection fibers 112 are coupled to protection linecards within network elements 104. Typically, protection linecards within network elements 104, as well as working linecards within network elements 104 which are not included in circuit path 124 of FIG. 1a, have no access to J1 information which is stored on control cards within network elements 104 included in circuit path 124. Without access to J1 information, J1 monitoring of the STS signal which passes through protection fibers 112 may not occur. As a result, the integrity of the STS may not be verified. In some cases, if the STS is sent to an incorrect network element 104 and when J1 monitoring does not occur, a customer may not detect that he is not receiving correct data. Neglecting to provide a customer with data he or she has requested, or inadvertently providing data to unscrupulous customers, may cause significant problems.
A network element within a BLSR may generally include working linecards, or input/output (I/O) cards, which are coupled to working fibers, and protection linecards which are coupled to protection fibers. FIG. 2 is a diagrammatic representation of a network element which is a part of a BLSR. A network element or node 204 includes working linecards 208a, 208b and protection linecards 208c, 208d. Linecards 208 are coupled to a control card 212 which may maintain information used by network element 204. By way of example, control card 212 may store a list of all J1 information which is expected to be received on, sent by, or pass through at least one working fiber 216 associated with network element 204.
Typically, when a circuit which includes network element 204 is provisioned, J1 information is broadcast such that control card 212 receives the J1 information. Control card 212 may then provide the J1 information to working linecards 208a, 208b. Hence, when an STS is sent across fiber 216a, for example, the J1 information embedded in the STS may be verified against J1 information stored on control card 212 when J1 monitoring is enabled. Control card 212 generally does not provider the J1 information to protection linecards 208c, 208d. As a result, if an STS is sent across one of protection fibers 220a, J1 monitoring is not possible.
In order to perform J1 monitoring, monitoring circuitry is generally included in each working linecard associated with a network element. FIG. 3 is a diagrammatic representation of a network element which is a part of a BLSR and includes components used to enable J1 monitoring. A network element 304 includes working linecards 308 and a control card 312. For ease of illustration, protection linecards within network element 304 have not been shown.
Substantially any linecard 308, e.g., linecard 308b, which is associated with a circuit in which J1 monitoring, which is typically set on a circuit basis, is allowed may include monitoring circuitry 324 which cooperates with software 328 to compare J1 information embedded within an STS which passes through a fiber 316 associated with linecard 308. Monitoring circuitry 324, which may include a processor (not shown) such as a central processing unit may facilitate the collection of J1 information and may cooperate with software 328 to compare J1 information which is expected by network element 304 against the J1 information obtained from an STS. The results of a comparison may be passed from software 328 to control card 312, e.g., for storage. The J1 information which is expected by network element 304, as previously mentioned, is maintained by control card 312 after the J1 information is effectively broadcast at the time circuits which include network element 304 are provisioned.
Monitoring display 332, which is coupled to control card 312, may retrieve information from control card 312 and display the information. Information retrieved from control card 312 may include J1 information which is expected by network element 304 and actual J1 information which is embedded in an STS. The use of monitoring display 332 enables a network administrator or other user to substantially verify the integrity of an STS signal which uses working fibers 316 when J1 monitoring is enabled.
With reference to FIG. 4, the steps associated with one method of sending an STS on a BLSR when J1 monitoring is enabled or selected, either manually or automatically, will be described. A process 400 begins at step 404 in which circuit provisioning in a BLSR is initiated. Initiating circuit provisioning generally includes identifying network elements which are to be included in a circuit. Once circuit provisioning is initiated, J1 information is sent to network elements included in the circuit in step 408. As will be understood by those skilled in the art, the J1 information may often be provided only to the linecards associated with working fibers of the circuit.
In step 412, an STS, which includes embedded J1 information, is sent from a “current” network element to an appropriate network element. By way of example, when the STS is initially being sent from a beginning or starting network element to a first intermediate network element in the circuit, the beginning network element may be the current network element while the first intermediate network element may be the appropriate network element. After the STS is sent, it is determined in step 416 whether the STS is received by the appropriate network element on a working fiber. In other words, it is effectively determined whether the STS has been switched to a protection fiber.
When it is determined in step 416 that the STS was received by the appropriate network element on a working fiber, then the indication is that the J1 trace may be monitored. Accordingly, in step 420, the J1 trace is monitored to verify the continuity of an overall circuit or working path which includes the working fiber. Verifying the continuity of the J1 trace typically includes comparing J1 information stored within the appropriate network element to the J1 information embedded in the STS. Once the continuity of the J1 trace is verified, it is determined in step 424 whether the STS has reached its end point, i.e., whether the STS has reached the network element at its destination within the BLSR ring. If it is determined that the STS has reached its end point, then the process of sending an STS on a BLSR is completed. Alternatively, if it is determined that the STS has not reached its end point, the process flow returns to step 412 in which the STS is sent to the next appropriate network element in the circuit.
Returning to step 416, when it is determined that the STS has not been received by the appropriate network element on a working fiber, then the implication is typically that the STS has been switched to a protection fiber. As such, the J1 trace associated with the STS may not be monitored, as protection linecards generally are not privy to J1 information. When the J1 trace may not be monitored, the integrity of the STS may not be determined. From step 416, if the indication is that the STS has been switched to a protection fiber, process flow proceeds to step 424 in which it is determined if the STS has reached its end point.
The ability to perform J1 monitoring such that a J1 trace may be monitored is crucial in many cases to assure the integrity of an STS. However, when an STS is sent over a protection circuit path, the ability to perform J1 monitoring over the entire circuit path is lost. As a result, the integrity of the STS may not be verified, and misconnections within a protection circuit path may occur such that the wrong data is sent to a customer, or data may be sent to the wrong customer.
Therefore, what is needed is a system which enables J1 monitoring to occur with respect to an STS that is transmitted across a protection path. That is, what is desired is a method and an apparatus which allows for path traces to be monitored regardless of whether the path traces are part of a signal that is transmitted across a working circuit path or a protection circuit path.